1. Field of the Invention
This invention relates to improvements in radio control systems, and more particularly to a control system of the type which facilitates timely reliable communications intership or between the ship and the harbor/shore facilities, and which facilitates intraship communications, as well.
2. Description of the Prior Art
Shipboard telecommunications is in an increasing state of development especially in view of the widespread availability and usage of digital electronics. One of the problems encountered in shipboard communications is the extremely hostile environment in which high frequency communications are conducted. The metal ship hull and structures act as reflectors to the signals, exaccerbating an already difficult communication situation. Not uncommonly, for example, even today ships at sea have periods of from several hours to days during which communications, if possible at all, are by way of CW Morse code. Thus, there have been many proposals for equipment to enable more reliable communications. One proposal is for so called automatic error request (ARQ) operations, in which a teletype over radio signal is transmitted, and as it is received, confirming signals are returned. Thus, whether or not the message has been received is known to the transmitting station.
Another system which has been receiving recent attention is selective calling techniques, especially such techniques which can be digitally implemented. Typically, a digital selective calling (DSELCALL) operation is as follows. A message is constructed having certain portions formatted in accordance with predefined codes. The first portion of the sequence presents a format specifier, such as a distress call, an all ships call, or the like. The second portion is the address of a ship or class of ships to which the message is intended. The third portion indicates the priority of the message, such as urgent, routine, safety, etc. The fourth portion is the identification of the sending station, and the fifth portion includes the messages or messages to be transmitted. The total length of the message may be of predefined length, for instance, of up to 90 characters, and may typically contain information regarding the type of distress, if a distress message is involved, for example, or other information, as needed. In addition, the message may be directive; for instance, the message may request the receiving station to receive an extended message from the transmitting station on another frequency, for example, by teletype over radio. In such case, the message may set forth frequencies on which the teletype message will be sent. When such a message is received, the radio operator will configure a receiver and transmitter to operate on the specified frequencies. Usually, an ARQ unit is associated with such teletype operations, so that as the teletype message is being transmitted and received, confirmation signals are being transmitted to insure correct reception of the signal.
Because of the increasing telecommunication needs of commercial ships, increasing numbers of radio equipment and the like are being installed on ships. Usually, for example, there are one or more high frequency transmitters and receivers, as well as one or more very high frequency transmitters and receivers. There are many subuses for the equipment, such as providing telephone patch service for the people on board, providing telegraph service, providing teletype service and receiving weather and other information, and providing other communications pertaining to the ship's operation and business.
In addition to communication requirements to locations outside the ship, included in the radio specifications of most ships, are certain sensor functions. For example, most ships include sensors for indicating the ship's speed, heading and position, as well as the state of the sea, the winds, the weather, and so forth. Often, it is desired to communicate this information to other locations, such as nearby ships, or to land based "home" stations.
Of particular interest to shipboard personnel is the effective signalling of alarms. Some alarms typically used are distress, distress relay, vital safety, urgent messages, important safety, routine business, routine, VHF selective ringer and so forth. It can be seen that depending upon the alarm, it may be desired that selected ones of the alarms be sounded or displayed, or not sounded or displayed, in certain areas, such as officer's quarters, the wheelhouse, the radio officer's quarters, as necessary. In addition, some alarms may need to be broadcast or rebroadcast (if, for example, the alarm is a distress call received from another ship which requires the alarm to be rebroadcast), to nearby ships or land stations, as required.
Typically, shipboard radio and electronic apparatuses are operated and maintained by a radio officer. Usually, the radio officer is charged with the duty to operate the equipment during normal hours and with the duties to maintain and repair the equipment during overtime or non-working hours. This schedule may be particularly expensive to the ship owners, especially if significant overtime is needed.
It is therefore desirable to provide a system by which the ship's radio and electronic equipment can be operated in a non-attended manner, or in a manner requiring minimum attention of the ship's personnel. However, as set forth above, the system must also be capable of making decisions, for instance, to rebroadcast alarms, to direct alarms to preselected shipboard locations, to receive certain communications for later review or dissemination, and the like.